Belastingadviseur gezocht voor advies to start my own business: Consultant

Plaats: Amsterdam

Gevraagde diensten: inkomstenbelasting, belastingadvies

Toelichting
Hallo,
Ik hoop dat is oke vragen in het Engels, als is een moeilijke vraag in het Nederlands te schriven.

Mijn vraag:
I would work as an independent consultant in 2018, from October to December, and then a few months in 2019. I would like to know what happen in terms of taxes when part of the year I've wok as independent and the other part of the year employed by a company. Here the details:
I have been working this year for a company under a 38 hours contract, my salary is about 3000 bruto/month. From October until December I will work as a contractor for a consultancy registered in the UK, but the work is in the Netherlands. The agreement will be 3 days a week, for an amount of about 4500 euros/month gross.
How much taxes will I need to pay a year, and what would be my aprox. netto as a zzpr? (taxes as an employee have been already deducted of course)
What type of cost can I deduct? Does the pension payment count? Besides phone, transport, and insurances I don't think it will be large costs.
When do I need to pay the taxes?
Any considerations I need to make as a zzpr?
Thank you in advance